110v sockets

[johnboy6083]

hi ladies and gents. Im currently in the process of fitting out a workshop for the firm i work for. I have a 3.5KVA 415/110v transformer, which feeds a 110v DB (converted 1ph DB).
The question i have is regarding cable sizing, and grouping in particular.
There are going to be 6 110V sockets. 16A @3m, 10m,15m and 40m. 32A@15m.
there is also going to be 3 flourescent lights fed from the trunking on 1 circuit.
my cable calcs say that for the 16A sockets apart from the 40m, will be ok @ 2.5mm2, providing the grouping is 3 or less. the 32A comes in @ 6mm, unless the grouping is more than 2.
If i oversize the cables for the other 6 circuits, in order that they never reach full opertaing temp, then will i, in your opinion be ok to keep the 32A socket on 6mm2 cable.

My theory is this, The fuse on the transformer is a 32A 88-1. if the 32A socket is ever used at its max rating, (i doubt there is much portable 110v gear availalable at that rating) then the other sockets being used will pop the fuse anyway. Also, as the sockets are for powertool use, they are run intermittantly, and never constantly, so the cable never has time to reach full operating temp, which means that they shouldnt have a detrimental effect on the other circuits.

 

[johnboy6083]

Ive just found a calcul;ation which will allow me to do as i thought. If your load is less than 0.3xItx Cg, then you can ignore that circuit for the purposes of grouping factors.

So, if i oversize my 16A sockets and run 6mm, with an It of 38A.
if i allow 10A per socket,
0.3x 38x 0.57 (grouping factor) = 6.156A.

So, going by this, i cannot neglect those circuits for grouping. I still think that these circuits will never be run at maximum, and will never all be at operating temperature at once.

 

[The Ranger]

Mate sometimes you've got to put the books down and go with what you know!